johnastovall
Deceased, but remembered fondly here...
" The following quantity limits apply to both your spare and installed batteries. The limits are expressed in grams of “equivalent lithium content.” 8 grams of equivalent lithium content is approximately 100 watt-hours. 25 grams is approximately 300 watt-hours:"
http://safetravel.dot.gov/whats_new_batteries.html
http://safetravel.dot.gov/whats_new_batteries.html